WebView do not inform UIDelegate in modal NSWindow

Question

I build a NSWindow with a WebView in it. The the WebView loads an HTML-Page with buttons calling the JacaScript-Functions "window.close()" and "window.open('URL')" by clicking on it.

The WebView notice this and informs my UIDelegate by calling the selectors:

- (WebView *)webView:(WebView *)sender createWebViewWithRequest:(NSURLRequest *)request;
- (void) webViewClose:(WebView *)sender;

This works fine until the NSWindow is displayed modal. If it is so, the UIDelegate won't be informed by the WebView on user interaction.

Can someone explain me why it made the differences between "Modal" and "Not Modal"??? And what do I do so that this also works modal?